Punk-Pop trio opens for role model and music pioneer Joan Jett

"I go back now and I sound like a chipmunk," Diaz said. "I can't believe they let me sing in their band. I can't believe how 'little' I sang."

Of course, Diaz was 13 at the time.

Now, her vocal style's size and her punk-pop band's raw power continue to maintain commercial consciousness for Girl in a Coma, a trio from San Antonio, Texas, that opens for role model Joan Jett and the Blackhearts on Saturday at Ironstone Amphitheatre in Murphys.

"I've been listening to her since I was 13," said Diaz, now 25, who plays guitar and sings with sister Phanie, 33, the drummer, and bassist Jenn Alva in Girl in a Coma. "Everything we've done ... is a lot similar to things she (Jett) had to face. When she had to face it, it was a lot harder. There wouldn't be music for us now if she hadn't been there."

Like Diaz, Jett was a teenager (17) when she and Sandy West formed the Runaways in 1975. They were pioneers of punk-rock and punk-pop, helping advance chances for young women in a male-dominated industry.

After learning to play rudimentary electric guitar, Diaz played two tunes - including "Stolen," one of her own - and was invited to join the band one week before her 14th birthday.

"I played it and they looked at each other and thought it was a cover tune," Diaz said with laugh. "I said, 'No, it's mine.' They said, 'You wanna be in our band?' It was so cool."

Diaz's mom, Maria Gonzalez, the secretary in a hospital's hyperbaric unit, introduced her to Jett's music: "I knew how powerful (Jett) was as one of the few 'she-male' musicians in such a masculine world."

Diaz, her sister and friend have added to that legacy with four albums, steady touring and, Saturday, their first show with Jett - they record for her Blackheart label - in a year.

When the "incredibly shy" Diaz discovered that sister Phanie had a band (Sylvia's Radio and Girl in a Coma prior to 2006), "I first got upset," Diaz said. Then Phanie "found me a guitar in a Dumpster. With a couple of strings on it. I was so happy."

Phanie "just taught me some power chords," Diaz said. "I practiced for hours and hours in the garage," writing "lots of songs about teenage depression. But I wanted to go out and back it up as an adult."

At 15, she played with older brother Nick (a bassist) at his graduation.

"I crossed my eyes when I looked at the microphone," she said. "I was super-nervous. I had low self-esteem."

"Huge" fans of the Smiths and Morrissey ("an amazing lyricist"), they're named after the Manchester, England band's "Girlfriend in a Coma" - as a "way to pay homage." Diaz loved guitarist Johnny Marr's style.

While "making mom not go crazy ... we'd make her get a credit card to pay for stuff," Diaz said. "She was so strong and supportive. Step-dad Margo took care of business at home.

Jett, now 54, keeps on role-modeling, as an artist, entertainer - despite just three top-10 singles in a 38-year career - and savvy business person.

"Me, I'm growing up," Diaz said. "Basically I've stopped all the childish things you say and do when you're in a band. I've owned up to all my mistakes and learned my lessons. I've tried to do things the positive way. Not the negative way. I'm not using anything for the bad."

Diaz and Girl in a Coma are trying to do something good.

Three years ago, their touring van was stopped by law enforcement on a Michigan highway.

"I was asleep," Diaz said. "The girls were angry. The (police) flashed their lights in there looking for somebody. They decided we had too much stuff in the back and randomly wanted to pick us up. Why?"

That heightened their awareness of Arizona Senate bill 1070, anti-immigration legislation passed in 2010. Diaz and Girl in a Coma participated in a community protest at Arizona's Maricopa County Prison.

That inspired her first socio-political song: "Hope."

"People hope for lots of change in the U.S., the 'land of the free,' " said Diaz, who was born in San Antonio. "When they come here, it's actually much worse than they think. It's not all Big Macs and (stuff). They just wanna take everything away."

The band has kept the Diaz sisters and Alva balanced.

"Yeah, sure," she said. "I've been doing this half my life, I know. It's amazing. We've gone through so much. So much stuff. That's what's kept us close. If one falls down, we all pick them up."